IOsub

IOsub is a conceptual framework used in computer science to model and analyze input/output subsystems within computing systems. It provides a structured way to examine how devices, buses, and data pathways interact and how software policies govern access to I/O resources. IOsub emphasizes the separation of concerns among hardware interfaces, data transport, buffering, and coordination logic, enabling systematic comparison of different I/O designs.

A typical IOsub architecture consists of several layers: an I/O interface layer that wraps device drivers and hardware adapters; a transport layer that manages data channels and bus protocols; a buffering and caching layer to absorb bursts and smooth latency; a scheduling or dispatch layer with policies for queueing and prioritization; a completion and notification layer that signals operation completion; and an error handling or recovery layer. Cross-cutting monitoring and observability components may be included to track performance and reliability.

In practice, IOsub supports multiple I/O models, including blocking and non-blocking I/O, synchronous and asynchronous operation, and event-driven completion. It helps reason about trade-offs such as latency versus throughput, locality, fairness across devices, backpressure, and energy use. Researchers use IOsub as a neutral frame to compare architectures like direct memory access, device-driver designs, and user-space I/O frameworks.

IOsub is not a standard or product but a pedagogical construct found in textbooks and research papers. It is used to illustrate design decisions and to highlight how component interactions affect performance. Real systems typically integrate several IOsub-like subsystems tuned for workload, hardware, and operating system policies. See also I/O scheduling, asynchronous I/O, device driver, and buffering.